The man reportedly bought the bottle before he went to school and became immediately unwell when he started drinking from it.

He is currently in a coma with severe injuries to his stomach and intestines.

"The boy had bought the bottle at a shop and drank from it at school. We have seized the entire shipment from where the bottle originated from for further investigations," Antwerp public prosecution official Dominique Reyniers said.

"A second bottle from that same shipment had already been sold. That was likewise recovered and appears to have contained normal mineral water."

The public prosecution office was initially keeping every option open because it was not immediately certain whether the ammonia was already in the bottle before the victim bought it.

However, the prosecution office later said the youth might have tried to commit suicide. He was reportedly suffering from personal problems.

Spadel, the company that owns subsidiary Spa, has been informed of the incident.